This invention relates generally to internal combustion engines, and, more particularly, to turbochargers used in conjunction with an internal combustion engine.
A limiting factor in the performance of an internal combustion engine is the amount of combustion air that can be delivered to the intake manifold for combustion in the engine cylinders. Atmospheric pressure is often inadequate to supply the required amount of air for proper operation of an engine.
An internal combustion engine, therefore, may include one or more turbochargers for compressing air to be supplied to one or more combustion chambers within corresponding combustion cylinders. The turbocharger supplies combustion air at a higher pressure and higher density than existing atmospheric pressure and ambient density. The use of a turbocharger can compensate for lack of power due to altitude, or to increase the power that can be obtained from an engine of a given displacement, thereby reducing the cost, weight and size of an engine required for a given power output.
A turbocharger typically includes a turbine driven by exhaust gases from the engine, and a compressor driven by the turbine. The compressor receives the air to be compressed and supplies the air to the combustion chamber. A common shaft interconnects the turbine wheel of the turbine with the compressor wheel in the compressor section. A stream of exhaust gases from the engine is conducted from the exhaust manifold to the turbine. The stream of exhaust gases passing through the turbine causes the turbine wheel to rotate, thereby turning the common shaft interconnecting the turbine wheel and the compressor wheel and rotating the compressor wheel.
Ambient air to be used for combustion in the internal combustion engine is brought into the compressor section, through an inlet for the compressor. The air is compressed by the compressor wheel, and is directed to the inlet manifold of the internal combustion engine.
Several problems are experienced with previously known constructions for turbochargers as described above. For instance, turbochargers generally take some time when increased power demands are placed on the system to gain speed and provide increased pressure. Therefore, when the motor is running under conditions which require quick acceleration, a delay period occurs while the turbocharger accelerates and desired instantaneous acceleration cannot be achieved.
One solution is described in U.S. Pat. No. 5,341,060 (Kawamura), entitled xe2x80x9cENGINE WITH A FLYWHEEL GENERATOR.xe2x80x9d According to Kawamura, providing a device for controlling a turbocharger with an electric rotary machine optimizes boost pressure, according to the depth to which an accelerator pedal is depressed. Specifically, a turbocharger, which is coupled to an internal combustion engine, is supplied with an electric rotary machine with a rotor. The rotary machine and rotor are coupled to a power converter, which in turn is joined to a battery. The rotary machine and rotor are battery powered when in a motor mode and supply power to the battery in a generator mode.
While Kawamura provides boost to the turbocharger, the Kawamura solution has limitations making it less effective. Reliance on a battery introduces problems, including poor cold weather performance, maintenance, weight, and short life span. These problems are accentuated with a power converter where additional power is lost. Moreover, Kawamura only provides an electrical connection, which is subject to corrosion and decay.
U.S. Pat. No. 4,312,183 (Regar) discloses an exhaust gas turbocharger for diesel engines including a turbocharger having a turbine and a compressor interconnected via a turboshaft. A flywheel separate from the turboshaft is selectively coupled and decoupled from a turboshaft using a freewheel or overriding clutch. A summation mechanism such as a planetary gear arrangement is interposed between the clutch and freewheel. Regar ""183 therefore provides an apparatus for mechanically interconnecting a freewheel with a turboshaft of a turbocharger.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, a turbocharger system for use in an internal combustion engine is provided with a turbocharger including a turbine, a compressor and a turboshaft coupling the turbine to the compressor. A first motor/generator is mechanically coupled to the turboshaft. A second motor/generator is mechanically coupled to a flywheel and is electrically coupled to the first motor/generator.
In another aspect of the invention, a method of powering a turbocharger system is provided with the steps of providing a turbocharger including a turbine, a compressor and a turboshaft coupling the turbine and the compressor together; mechanically coupling a first motor/generator to the turboshaft; mechanically coupling a second motor/generator to a flywheel; electrically coupling the second motor/generator to the first motor/generator; storing power in the flywheel using the second motor/generator during periods of excess turbocharger boost; and rotating the turbocharger shaft using the first motor/generator during periods of insufficient turbocharger boost.